Soft decision decoding method and system thereof

ABSTRACT

Method and system for soft decision decoding are provided. A soft decision decoding method implemented by a receiver in a communication network may include: receiving a signal frame carrying a message through a communication network; obtaining data structure of the message; obtaining at least one bit of the message based on the data structure and known information; and decoding the received signal frame based on the at least one bit using soft decision decoding to obtain a decoding result. Decoding efficiency and accuracy may be improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to PCT Patent ApplicationPCT/CN2013/082533, filed on Aug. 29, 2013, and entitled “SOFT DECODINGMETHOD AND SYSTEM THEREOF”, and the entire disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to soft decision decoding of asignal frame received in a communication network.

BACKGROUND

In communication systems, soft decision decoding methods are widely usedat a receiver side to decode a bit sequence which is encoded at atransmitter side, thereby obtaining information from the transmitterside. Due to channel fading, shadowing, interferences and the like,error rates of conventional soft decision decoding methods may be high.

SUMMARY

Inventors found that some bits of a message sent from a transmitter to areceiver may be already known to the receiver. Using these known bits toperform soft decision decoding can improve decoding efficiency andreduce error rate.

In one embodiment, a soft decision decoding method implemented by areceiver is provided. The method may include: receiving a signal framecarrying a message through a communication network; obtaining datastructure of the message; obtaining at least one bit of the messagebased on the data structure and known information; and decoding thereceived signal frame based on the at least one bit using soft decisiondecoding to obtain a decoding result.

In some embodiments, the message may contain the known information.

In some embodiments, the at least one bit may be distributedsubstantially evenly in the received signal frame.

In some embodiments, the data structure may be obtained based on thelength of the signal frame. In some communication networks, such as avehicle safety communication (VSC) network, there are only a few typesof messages. Based on the length of the signal frame, the message typemay be determined, thus the data structure may be obtained.

In some embodiments, the data structure of the message may be obtainedbased on control information of the message. The control information mayindicate some basic information of the message, which may be used todetermine the data structure of the message.

In some embodiments, if the communication network is an IEEE 802.11pnetwork, obtaining the data structure of the message may include:obtaining a physical layer convergence protocol (PLCP) headercorresponding to the message; determining which type of message themessage is based on control information of the message contained in thePLCP header; and obtaining the data structure of the message based onthe determined message type. In the IEEE 802.11p network, the controlinformation of the message may be contained in the PLCP header, and thesignal frame may carry the PLCP header and the message. The PLCP headermay be decoded prior to the message. Therefore, the data structure maybe obtained before decoding of the message. In some embodiments, whichtype of message the message is may be determined based on payload lengthinformation in the PLCP header.

In some embodiments, determining the message type may include:determining whether the PLCP header includes information directlyindicating the message type; and if yes, determining the message typebased on the information directly indicating the message type.

In some embodiments, a bit in a “Reserved” field of the PLCP header maybe used to indicate whether or not the PLCP header includes theinformation directly indicating the message type, last few bits in a“RATE” field and/or a “LENGTH” field may be used to directly indicatethe message type. In some embodiments, if a value of the “Reserved”field indicates that the PLCP header includes information directlyindicating the message type, which type the message is may be determinedbased on a value of the “Rate” field.

In some embodiments, if the data structure of the message indicates thatthe message is a basic safety message (BSM), the at least one bit mayinclude positioning data of the receiver. The BSM may includepositioning data of a transmitter which sent the signal frame. Since theeffective range of vehicular communication may be short, for examplewithin about 300 meters, first few digits of the positioning data, suchas latitude and longitude position, of the transmitter and the receivermay be the same. Therefore, the at least one bit may represent the firstfew digits of the positioning data of the receiver, and may equal tosome corresponding bits in the message which represent correspondingfirst few digits of the positioning data of the transmitter. In someembodiments, the at least one bit may include bits representing thefirst few digits of the positioning data, sub-network access protocol(SNAP) header data and logical link control (LLC) header date in amedium access control (MAC) layer of the receiver, and any combinationthereof. According to IEEE 802.11p, the SNAP header data and the LLCheader data may be set as default values, which means they are known tothe receiver.

In some embodiments, decoding the received signal frame based on the atleast one bit using soft decision decoding may include: generating apriori sequence which includes N likelihood ratios each of whichcorresponds to one bit of the message, where likelihood ratioscorresponding to the at least one bit may be set according to the atleast one bit; and decoding the received signal frame based on thepriori sequence using soft decision decoding.

In some embodiments, the priori sequence may be a log likelihood ratio(LLR) sequence.

In some embodiments, the method may further include transmitting thedecoding result to an application layer even if the decoding resultincludes an error. Each bit of the decoding result may represent aprobability of the corresponding bit being “1” or “0”. Therefore,threshold values may be set to pick up some bits having highprobabilities of being “1” or “0”, and these bits may be used in theapplication layer.

In one embodiment, a soft decision decoding system in a receiver isprovided. The system may include a transceiver configured to receive asignal frame carrying a message through a communication network. Thesystem may further include a processing device configured to: obtaindata structure of the message; obtain at least one bit of the messagebased on the data structure and known information; and decode thereceived signal frame based on the at least one bit using soft decisiondecoding to obtain a decoding result.

In some embodiments, the message may contain the known information.

In some embodiments, the at least one bit may be distributedsubstantially evenly in the received signal frame.

In some embodiments, the processing device may be configured to obtainthe data structure based on the length of the signal frame.

In some embodiments, the processing device may be configured to obtainedthe data structure based on control information of the message.

In some embodiments, if the communication network is an IEEE 802.11pnetwork, the processing device may be configured to obtain the datastructure by: obtaining a physical layer convergence protocol (PLCP)header corresponding to the message; determining which type of messagethe message is based on control information of the message contained inthe PLCP header; and obtaining the data structure of the message basedon the determined message type. In some embodiments, which type ofmessage the message is may be determined based on payload lengthinformation in the PLCP header.

In some embodiments, the processing device may be configured todetermine the message type by: determining whether the PLCP headerincludes information directly indicating the message type; and if yes,determining the message type based on the information directlyindicating the message type. In some embodiments, the processing devicemay be configured to determine whether the PLCP header includes theinformation directly indicating the message type based on a value of a“Reserved” field of the PLCP header, and determine which type of messagethe message is based on a value of a “RATE” field and/or a “LENGTH”field if the value of the “Reserved” field indicate that the PLCP headerincludes the information directly indicating the message type.

In some embodiments, if the data structure of the message indicates thatthe message is a basic safety message (BSM), the at least one bit mayinclude positioning data of the receiver. In some embodiments, the atleast one bit may include bits representing first few digits of thepositioning data of the receiver, sub-network access protocol (SNAP)header data and logical link control (LLC) header date in a mediumaccess control (MAC) layer of the receiver, and any combination thereof.

In some embodiments, the processing device may be configured to decodethe message based on a priori sequence which may include N likelihoodratios each of which corresponds one bit of the message using softdecision decoding, where likelihood ratios corresponding to the at leastone bit may be set according to the at least one bit.

In some embodiments, the priori sequence may be a log likelihood ratio(LLR) sequence.

In some embodiments, the processing device may be further configured tosend the decoding result to an application layer even if the decodingresult includes an error.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several embodiments in accordance with thedisclosure and are, therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings.

FIG. 1 schematically illustrates a flow chart of a method forcommunicating a vehicle safety message in a vehicle network according toone embodiment;

FIG. 2 schematically illustrates a process of generating a first bitsequence carrying a basic safety message (BSM);

FIG. 3 schematically illustrates contents of a BSM in ASN.1 (abstractsyntax notion one) encoding;

FIG. 4 illustrates a conventional structure of a physical layerconvergence protocol (PLCP) header according to IEEE 802.11p;

FIG. 5 illustrates a redefined physical layer convergence protocol(PLCP) header according to one embodiment;

FIG. 6 schematically illustrates conversion from a second bit sequenceto orthogonal frequency division multiplexing (OFDM) symbols;

FIG. 7 is a diagram schematically illustrating a soft decision decodingprocess according to one embodiment; and

FIG. 8 schematically illustrates a block diagram of a soft decisiondecoding system in a receiver according to one embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here. It will be readily understood that the aspects of thepresent disclosure, as generally described herein, and illustrated inthe Figures, can be arranged, substituted, combined, and designed in awide variety of different configurations, all of which are explicitlycontemplated and make part of this disclosure.

FIG. 1 schematically illustrates a flow chart of a method 100 forcommunicating a vehicle safety message in a vehicle network according toone embodiment.

Standard IEEE 802.11p defines communication architectures for wirelessaccess in vehicular environments (WAVE), especially for mechanisms inmedium access control (MAC) layers and physical layers. Communicationsof messages in vehicle networks are compatible with IEEE 802.11p.However, conventional communication methods in vehicle networks may havehigh packet loss rates due to decoding failures, which is extremelyunsatisfactory for vehicle safety messages. Hereunder, communication ofa vehicle safety message in a vehicle network will be illustrated.Extensions to communications of other messages in other communicationnetworks may be easily conceived.

In S101, generating a first bit sequence containing a vehicle safetymessage.

Vehicle safety messages may include various messages which may havedifferent names and/or contents in different regions according tospecific local agreements. For example, vehicles may send their basicstate information using basic safety message (BSM) in USA. Foradditional collision avoidance applications, signal phase and timing(SPAT) messages and map data (MAP) messages may be sent to convey thesignal state and geographical description of an intersection. While inEurope, cooperative awareness messages (CAM) and decentralizedenvironmental notification messages (DENM) may be used.

Hereunder, communication of a BSM, which may happen most frequently inUSA, will be illustrated as an example.

FIG. 2 schematically illustrates a process of generating the first bitsequence containing the BSM. According to IEEE 802.11p, the BSM may betransmitted as WAVE short message (WSM) data using WAVE short messageprotocol (WSMP). Referring to FIG. 2, the BSM may be generated fromapplications in an application layer and carried in a “WSM data” field.Thereafter, the WSM data may pass through a WSMP layer, in which the WSMdata is appended with a WSMP header to form a WAVE short message. TheWAVE short message may reach a logic link control (LLC) layer, in whichthe WAVE short message may be appended with a sub-network accessprotocol (SNAP) header and a LLC header. The WAVE short message appendedwith the SNAP header and the LLC header is to be transmitted into a MAClayer, thus normally called as a MAC service data unit (MAC SDU). In theMAC layer, the MAC SDU may be appended with a MAC header to form the MACprotocol data unit (MAC PDU), such that the first bit sequencecontaining the BSM is formed. According to IEEE 802.11p, a frame checksequence (FCS) may be generated based on the MAC PDU and appended to it,which may be used in a following FCS check process.

Generating the MAC PDU is well known in the art and may not be describedin detail here. The formed MAC PDU may be then sent to a physical layerto be encoded and modulated therein.

Inventors found that, in WAVE systems, at least one bit of the MAC PDUmay be already known to potential receivers, which may facilitatesubsequent decoding at the receiver side.

Firstly, some reserved fields and/or invariant fields in the MAC PDU maybe set as default values in some occasions. For example, in collisionavoidance applications, SNAP headers, LLC headers, etc., for BSMmessages may have a fixed value according to the standard.

Secondly, the transmitter and the potential receivers may share someidentical data in the “WSM data” field according to the message type.FIG. 3 schematically illustrates contents of a BSM in ASN.1 (abstractsyntax notion one) encoding. As shown in FIG. 3, the BSM reserves 4bytes, 4 bytes and 2 bytes respectively for representing latitude,longitude and elevation information of the transmitter. Since theeffective range of vehicular communication may be short, normally withinabout 300 meters, it could be concluded that first few digits of thepositioning data of the transmitter and the receiver may be the same.

The at least one bit of the MAC PDU can be used by the receiver todecode data packages sent by the transmitter, thereby improving thedecoding rate, which will be illustrated subsequently.

In some embodiments, a first set of bits which may be known to thereceiver may be selected and distributed in the MAC PDU according to apredetermined rule. For example, the first set of bits may be evenlydistributed in the MAC PDU, for further benefiting the subsequentdecoding. Distributing the first set of bits may be simply achievedusing an interleaver.

In S103, appending the first bit sequence with a physical layerconvergence protocol (PLCP) header to form a second bit sequence.

The PLCP header may include control information of the first bitsequence, such as modulation type, encoding rate, payload length, etc.FIG. 4 illustrates a conventional structure of a PLCP header accordingto IEEE 802.11p. In the conventional PLCP header structure, a “RATE”field having 4 bits may represent the transmission rate, a “LENGTH”field having 12 bits may represent the payload length, and a 1 bit“Reserved” field is reserved for other applications. According to thestandard, the current transmission rate for vehicle safety messages isconfined to a few options. Therefore, some bits in the 4-bit “RATE”field may be spare. Further, safety related messages are relativelyshorter in message size, so that the 12-bit “LENGTH” field may be alittle wasteful for only representing the payload length. Therefore,some spare bits within the “RATE” field and the “LENGTH” field, and the1 bit in the “Reserved” field may be used for other purposes.

As illustrated above, the first set of bits which are known to thereceiver may change based on message types. Therefore, in someembodiments, the original PLCP header may be redefined to indicate themessage type. If the receiver can obtain the redefined PLCP header, themessage type may be identified, such that the receiver may obtain thefirst set of bits of the MAC PDU.

FIG. 5 illustrates a redefined PLCP header according to one embodiment.As shown in FIG. 5, (4-x) bits (x<4, for example, 1 or 2) within the“RATE” field and (12-y) bits (y<12) within the “LENGTH” field may beused as a “PATTERN1” field and a “PATTERN2” field for representing themessage type which indicates what kind of message the first bit sequencecarries. The remained x bits within the “RATE” field and y bits withinthe “LENGTH” may be used for indicating the transmission rate andpayload length, as they are originally defined. Further, the 1-bit inthe “Reserved” field may be utilized as a “SWITCH” identifier indicatingwhether a message type field is included in the PLCP header. With thisredefinition, the total length of the PLCP header remains unchangedcompared with the conventional one, thereby still being compatible withthe IEEE 802.11p standard.

In some embodiments, the PLCP header may further include, by using sparebits, a redistribution identifier for indicating whether the first setof bits are redistributed in the MAC PDU and how they are distributed.

It should be noted that redefining the PLCP header may be optional.

In S105, encoding and modulating the second bit sequence into a signalframe.

The second bit sequence containing the BSM needs to be encoded andmodulated into digital symbols, for example, orthogonal frequencydivision multiplexing (OFDM) symbols, to increase data rate. Encodingand modulating the second bit sequence may be implemented by mechanismsin the physical layer, including scrambler, encoder, interleaver,mapper, OFDM symbol assembler, inverse fast Fourier transmitter (IFFT)and spectral shaping.

FIG. 6 schematically illustrates conversion from the second bit sequenceto the OFDM symbols. As shown in FIG. 6, the MAC PDU in the second bitsequence, together with a “SERVICE” field of the PLCP header, a “Tail”field and some pad bits, may be encoded and modulated into several OFDMsymbols, constituting a “DATA” part. The PLCP header, except its“SERVICE” field, may be encoded and modulated into OFDM symbols,constituting a “SIGNAL” part. According to IEEE 802.11p, modulation typeand encoding rate of the PLCP header are confined to BPSK 1/2.Information of modulation type and encoding rate of the MAC PDU appendedwith the “SERVICE” field may be carried in the “SIGNAL” part as it iscontained in the PLCP header. Further, a PLCP preamble with 12 symbolsmay be appended.

After digital-to-analogue conversion, the OFDM symbols may be convertedinto a signal frame ready to be sent out.

In S107, sending the signal frame.

The signal may be sent, for example, broadcasted, by a transceiver inthe physical layer of the transmitter through the vehicle network.

Above described S101 to S107 are implemented at the transmitter side.

Following processing goes to a receiver side.

In S201, receiving the signal frame.

Receiving the signal frame may be implemented in a physical layer of thereceiver. Theoretically, all neighboring vehicles within the effectiverange may receive the signal frame through the vehicle network. However,in practise, signal transmission may be blocked by obstacles. Besides,the received signal frame may be corrupted by noise and interference.

In S203, obtaining the PLCP header.

By analogue-to-digital conversion and synchronization, the signal framemay be converted into the digital symbols which include the “SIGNAL”part and the “DATA” part. The “SIGNAL” part may be then demodulated anddecoded to obtain the PLCP header.

The PLCP header may include control information of the MAC PDU, whichcontrol information may be essential for subsequent decoding. In thevehicle network, correctly obtaining the PLCP header may be ensured bymultiple iterations.

In S205, obtaining data structure of the first bit sequence.

The data structure may indicate the length, data field distribution, andthe like of the first bit sequence, which is important for decoding the“DATA” part to obtain the first bit sequence.

The data structure may be corresponding to the message type of themessage contained in first bit sequence. Therefore, the data structuremay be obtained based on the message type.

In some embodiments, the decoded PLCP header may be checked to determinewhether the PLCP header has been redefined to include the message type.Specifically, whether the “Reserved” field is used as a “SWITCH”identifier in the decoded PLCP header may be checked. If the checkresult is “yes”, for example, the bit in the “Reserved” identifier is“1”, the “PATTERN 1” and/or “PATTERN 2” fields should be checked toidentify the message type. Based on the message type, the data structureof the first bit sequence may be obtained.

As described above, redefining the PLCP header may be optional, whichmeans the decoded PLCP header may not include the message typeinformation directly. Therefore, checking whether the PLCP header hasbeen redefined may be optional. The message type may be estimated basedon other information.

In some embodiments, which type of message the message contained in thefirst bit sequence is may be determined based on data in the “LENGTH”field. The “LENGTH” field may stand for the payload length. Sincedifferent types of messages transmitted in vehicle networks may havedifferent corresponding payload lengths, respectively, the message typemay be determined based on the data in the “LENGTH” field.

In some embodiments, the message type may be determined based on data inthe “RATE” field and length of the “DATA” part of the digital symbols.The “RATE” field and length of the “DATA” part may also used todetermine the length of the first bit sequence.

In some embodiments, the message type may be determined directly basedon the length of the signal frame.

In some embodiments, the data structure may further include informationof how the first set of bits being distributed in the first bitsequence, which information may be obtained based on the PLCP header.

In S207, obtaining at least one bit of the first bit sequence based onthe data structure and known information.

Based on the data structure, which kind of data fields are contained inthe first bit sequence may be known. As described above, someinformation contained in the first bit sequence may be already known tothe receiver. For example, the first bit sequence contains the BSM, thussome positioning information together with some header data informationof the transmitter may be known to the receiver. Therefore, at least onebit of the first bit sequence may be obtained based on the datastructure and the known information.

In some embodiments, a second set of bits which correspond to the firstset of bits may be obtained. In some embodiment, a register may bededicated for obtaining the second set of bits. In some embodiments, thesecond set of bits may include bits representing first few digits of thepositioning data of the receiver. The first few digits of thepositioning data of the receiver and the transmitter may be the same. Insome embodiments, the second set of bits may include bits representingthe first few digits of the positioning data of the receiver, SNAPheader data and LLC header data in a MAC layer of the receiver, or anycombination thereof.

In S209, decoding the received signal frame based on the at least onebit using soft decision decoding.

In some embodiments, since the “SIGNAL” part of the signal frame isalready obtained, S209 may include decoding the “DATA” part of thesignal frame.

FIG. 7 is a diagram schematically illustrating a soft decision decodingprocess which is commonly applied in WAVE systems. Referring to FIG. 7,a decoder, such as a soft output viterbi algorithm (SOVA) or aBahl-Cocke-Helinek-Raviv algorithm (BCJR) decoder, may be input withpriori sequence and received encoded bits, thereby obtaining a decodingresult. The priori sequence may include N likelihood ratios, where N mayequal to a number of bits included in the decoding result, which may beobtained based on the data structure. Each of the likelihood ratios mayrepresent a probability value of a corresponding bit in the decodingresult, where the probability value may represent whether thecorresponding bit is like to be “0” or “1”.

In some embodiments, a log likelihood ratio (LLR) sequence, which is akind of priori sequence, may be formed based on the second set of bits.Specifically, each bit of the LLR sequence may represent a possibilityof a corresponding bit in the first bit sequence being “1” or “0”. TheLLR sequence may be calculated based on Equation (1):

$\begin{matrix}{{{{LLR}(k)} = {\log \frac{P\left( {{xk} = 1} \right)}{P\left( {{xk} = 0} \right)}}},} & {{Equation}\mspace{14mu} (1)}\end{matrix}$

where LLR(k) stands for a LLR value corresponding to a k^(th) bit in thefirst bit sequence, P(xk=1) stands for a probability of the k^(th) bitbeing “1”, and P(xk=0) stands for a probability of the k^(th) bit being“0”.

From Equation (1), it could be concluded as follows. When LLR(k)approaches “−∞”, it may indicate most possibility of the k^(th) bitbeing “1”. When the LLR(k) approaches “−∞”, it may indicate mostpossibility of the k^(th) bit being “0”. And when the LLR(k) equals to“0”, it may indicate that the k^(th) bit may have 50% chance of being“1” or “0”.

Normally, the likelihood ratio values may be normalized into [0, 1],where “0” may correspond to “−∞” calculated based on Equation (1), “1”may correspond to “+∞” calculated based on Equation (1) and “0.5” maycorrespond to “0” calculated based on Equation (1), such that a bit “0”of the LLR sequence may represent a corresponding bit of the first bitsequence definitely being “0”, and a bit “1” of the LLR sequence mayrepresent a corresponding bit of the first bit sequence definitely being“1”.

If the first bit sequence is completely unknown to the receiver, allLLRs in the LLR sequence may be set as “0.5”. However, as describedabove, the at least one bit of the first bit sequence may be known tothe receiver. Therefore, LLRs corresponding to the at least one bit maybe set according to the at least one bit, which may improve decodingefficiency and accuracy.

In some embodiments, a first set of LLRs corresponding to the second setof bits may be set as “1” or “0” according to the second set of bits.The first set of LLRs correspond to the second set of bits may bedistributed in the LLR sequence based on the data structure of the firstbit sequence, since the second set of bits may correspond to the firstset of bits.

The LLR sequence may be inputted into a soft output decoder togetherwith the “DATA” part of the signal frame to obtain a decoding result. Inthe decoding result which is also a LLR sequence, LLRs other than thefirst set of LLRs may no longer be “0.5”, but approach either “0” or“1”. In some embodiments, at least one iteration may be used in the softdecision decoding process, such that the LLRs other than the first setof LLRs may be more close to either “0” or “1”, which means whether acorresponding bit of the first bit sequence is “0” or “1” is morecertain.

The decoding result may be checked based on the FCS. If the decodingresult includes no error, the decoding result may be transmitted intolayers higher than the physical layer of the receiver, and the BSMcontained in the decoding result may be obtained and analyzed toestimate whether a dangerous driving state exists. If the decodingresult is checked to include an error, the decoding result may also betransmitted into the higher layers, for example, an application layer.Threshold values may be set to pick up some bits having highprobabilities of being “1” or “0”, and these bits may be used in theapplication layer.

According to one embodiment, a soft decision decoding system 300 isprovided. The soft decision decoding system 300 may be disposed at areceiver side in a communication network. FIG. 8 schematicallyillustrates a block diagram of the soft decision decoding system 300.

Referring to FIG. 8, the soft decision decoding system 300 may include atransceiver 301 configured to receive a signal frame carrying a messagethrough the communication network. The soft decision decoding system 300may further include a processing device 303 configured to: obtain datastructure of the message; obtain at least one bit of the message basedon the data structure and known information; and decode the receivedsignal frame based on the at least one bit using soft decision decoding.

Detail configurations of the processing device 303 may be obtained byreferring detail descriptions in S203 to S209, which may not beillustrated in detail here.

There is little distinction left between hardware and softwareimplementations of aspects of systems; the use of hardware or softwareis generally a design choice representing cost vs. efficiency tradeoffs.For example, if an implementer determines that speed and accuracy areparamount, the implementer may opt for a mainly hardware and/or firmwarevehicle; if flexibility is paramount, the implementer may opt for amainly software implementation; or, yet again alternatively, theimplementer may opt for some combination of hardware, software, and/orfirmware.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

1. A method for decoding data, comprising: receiving a signal framecarrying a message through a communication network; obtaining datastructure associated with the message; obtaining at least one bit of themessage based on the data structure; and decoding the received signalframe based on the at least one bit using soft decision decoding toobtain a decoding result.
 2. The method according to claim 1, whereinthe data structure is obtained based on the length of the signal frame.3. The method according to claim 1, wherein the data structure isobtained based on control information associated with the message. 4.The method according to claim 1, wherein the communication network is anIEEE 802.11p network, and obtaining the data structure associated withthe message comprises: obtaining a physical layer convergence protocol(PLCP) header corresponding to the message; determining a message typeassociated with the message based on control information associated withthe message contained in the PLCP header; and obtaining the datastructure associated with the message based on the message type.
 5. Themethod according to claim 4, wherein determining the message typecomprises: determining that the PLCP header comprises informationdirectly indicating the message type; and determining the message typebased on the information directly indicating the message type.
 6. Themethod according to claim 1, wherein, if the data structure associatedwith the message indicates that the message is a basic safety message(BSM), then the at least one bit comprises positioning data associatedwith a receiver.
 7. The method according to claim 1, wherein, if thedata structure associated with the message indicates that the message isa BSM, then the at least one bit comprises at least one of bitsrepresenting positioning data associated with a of the receiver,sub-network access protocol (SNAP) header data, and logical link control(LLC) header date in a medium access control (MAC) layer of thereceiver.
 8. The method according to claim 1, wherein decoding thereceived signal frame based on the at least one bit using soft decisiondecoding comprises: generating an priori sequence that includes Nlikelihood ratios, wherein each likelihood ratio corresponds to one bitof the message, and wherein likelihood ratios corresponding to the atleast one bit are set according to the at least one bit; and decodingthe received signal frame based on the priori sequence using softdecision decoding.
 9. The method according to claim 8, wherein thepriori sequence comprises a log likelihood ratio (LLR) sequence.
 10. Themethod according to claim 1, further comprising transmitting thedecoding result to an application layer.
 11. A soft decision decodingsystem implemented in a receiver, the system comprising: a transceiverconfigured to receive a signal frame carrying a message through acommunication network; and a processing device configured to: obtain adata structure associated with the message; obtain at least one bit ofthe message based on the data structure and decode the signal framebased on the at least one bit using soft decision decoding to obtain adecoding result.
 12. The soft decision decoding system according toclaim 11, wherein the processing device is configured to obtain the datastructure based on the length of the signal frame.
 13. The soft decisiondecoding system according to claim 11, wherein the processing device isconfigured to obtain the data structure based on control informationassociated with the message.
 14. The soft decision decoding systemaccording to claim 11, wherein the communication network is an IEEE802.11p network, and the processing device is configured to obtain thedata structure by: obtaining a physical layer convergence protocol(PLCP) header corresponding to the message; determining a message typeassociated with the message based on control information associated withthe message contained in the PLCP header; and obtaining the datastructure associated with the message based on the message type.
 15. Thesoft decision decoding system according to claim 14, wherein theprocessing device is configured to determine the message type by:determining that the PLCP header comprises information directlyindicating the message type; and determining the message type based onthe information directly indicating the message type.
 16. The softdecision decoding system according to claim 11, wherein, if the datastructure associated with the message indicates that the message is abasic safety message (BSM), then the at least one bit comprisespositioning data associated with a.
 17. The soft decision decodingsystem according to claim 11, wherein, if the data structure associatedwith the message indicates that the message is a BSM, then the at leastone bit comprises at least one of bits representing positioning dataassociated with a of the receiver, sub-network access protocol (SNAP)header data, and logical link control (LLC) header date in a mediumaccess control (MAC) layer of the receiver.
 18. The soft decisiondecoding system according to claim 11, wherein the processing device isconfigured to decode the message based on a priori sequence thatcomprises N likelihood ratios, wherein each likelihood ratio correspondsto one bit of the message, and wherein likelihood ratios correspondingto the at least one bit are set according to the at least one bit. 19.The soft decision decoding system according to claim 18, wherein thepriori sequence comprises a log likelihood ratio (LLR) sequence.
 20. Thesoft decision decoding system according to claim 11, wherein theprocessing device is configured to transmit the decoding result to anapplication layer.